Narrative:

Cleared for takeoff on runway 32L with instructions to not delay turn to 330 degrees for departure vectors. Made rolling takeoff from 90 degrees (perpendicular) taxiway. After takeoff, turned to 330 degrees on HSI compass card. Shortly after turn, departure asked us our heading. We replied, '330 degrees.' we were told to turn to 340 degrees and then that it appeared we were heading 270 degrees and to continue turn to 360 degrees. We x-chked the whiskey compass which verified departure's statement that we appeared to be heading 270 degrees. Both slaved compass systems showed the same 60 degree heading error. After the first officer attempted to reslave both compasses several times, we were abe to get normal indications. The departure was continued and the compass systems were true for the remainder of the flight. How the problem arose remains a mystery. After getting squared away, I asked the #1 F/a to check the cabin for people using unauthorized electronic equipment. After checking, she said that a few 'walkman' type pieces were being used, but only to play tapes. She also said that it was possible that someone using unauthorized equipment could have stopped using it and stowed it out of sight when she was walking down the isle obviously looking for something. At the gate the compasses were indicating 10 degree difference, which is not abnormal at that gate. During taxi-out, the compasses were within 1 or 2 degrees of each other. During the lineup maneuver, we made 2 close coupled 90 degree turns, left then right, into a rolling takeoff, which we were asked not to delay. Neither the first officer nor I can remember checking compass alignment with runway heading during the takeoff roll, possible because the #2 egt high light illuminated during the takeoff roll, distracting us a bit. After landing we wrote up the discrepancy in the aircraft logbook, and I spoke with the mechanic telling him that I had no idea what the problem could be or if it was an anomaly or if it was something we as a crew caused. The crew spent quite a bit of time, once we were at cruise altitude, discussing the incident and could not arrive at a logical explanation of the occurrence. In the future, however, we all agreed that closer attention should be paid to an extremely reliable system. Take nothing for granted.

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Original NASA ASRS Text

Title: WDB CREW HAS 60 DEGREE HEADING ERROR ON HIS AFTER TKOF.

Narrative: CLRED FOR TKOF ON RWY 32L WITH INSTRUCTIONS TO NOT DELAY TURN TO 330 DEGS FOR DEP VECTORS. MADE ROLLING TKOF FROM 90 DEGS (PERPENDICULAR) TXWY. AFTER TKOF, TURNED TO 330 DEGS ON HSI COMPASS CARD. SHORTLY AFTER TURN, DEP ASKED US OUR HDG. WE REPLIED, '330 DEGS.' WE WERE TOLD TO TURN TO 340 DEGS AND THEN THAT IT APPEARED WE WERE HDG 270 DEGS AND TO CONTINUE TURN TO 360 DEGS. WE X-CHKED THE WHISKEY COMPASS WHICH VERIFIED DEP'S STATEMENT THAT WE APPEARED TO BE HDG 270 DEGS. BOTH SLAVED COMPASS SYSTEMS SHOWED THE SAME 60 DEG HDG ERROR. AFTER THE F/O ATTEMPTED TO RESLAVE BOTH COMPASSES SEVERAL TIMES, WE WERE ABE TO GET NORMAL INDICATIONS. THE DEP WAS CONTINUED AND THE COMPASS SYSTEMS WERE TRUE FOR THE REMAINDER OF THE FLT. HOW THE PROB AROSE REMAINS A MYSTERY. AFTER GETTING SQUARED AWAY, I ASKED THE #1 F/A TO CHK THE CABIN FOR PEOPLE USING UNAUTH ELECTRONIC EQUIP. AFTER CHKING, SHE SAID THAT A FEW 'WALKMAN' TYPE PIECES WERE BEING USED, BUT ONLY TO PLAY TAPES. SHE ALSO SAID THAT IT WAS POSSIBLE THAT SOMEONE USING UNAUTH EQUIP COULD HAVE STOPPED USING IT AND STOWED IT OUT OF SIGHT WHEN SHE WAS WALKING DOWN THE ISLE OBVIOUSLY LOOKING FOR SOMETHING. AT THE GATE THE COMPASSES WERE INDICATING 10 DEG DIFFERENCE, WHICH IS NOT ABNORMAL AT THAT GATE. DURING TAXI-OUT, THE COMPASSES WERE WITHIN 1 OR 2 DEGS OF EACH OTHER. DURING THE LINEUP MANEUVER, WE MADE 2 CLOSE COUPLED 90 DEG TURNS, LEFT THEN RIGHT, INTO A ROLLING TKOF, WHICH WE WERE ASKED NOT TO DELAY. NEITHER THE F/O NOR I CAN REMEMBER CHKING COMPASS ALIGNMENT WITH RWY HDG DURING THE TKOF ROLL, POSSIBLE BECAUSE THE #2 EGT HIGH LIGHT ILLUMINATED DURING THE TKOF ROLL, DISTRACTING US A BIT. AFTER LNDG WE WROTE UP THE DISCREPANCY IN THE ACFT LOGBOOK, AND I SPOKE WITH THE MECH TELLING HIM THAT I HAD NO IDEA WHAT THE PROB COULD BE OR IF IT WAS AN ANOMALY OR IF IT WAS SOMETHING WE AS A CREW CAUSED. THE CREW SPENT QUITE A BIT OF TIME, ONCE WE WERE AT CRUISE ALT, DISCUSSING THE INCIDENT AND COULD NOT ARRIVE AT A LOGICAL EXPLANATION OF THE OCCURRENCE. IN THE FUTURE, HOWEVER, WE ALL AGREED THAT CLOSER ATTN SHOULD BE PAID TO AN EXTREMELY RELIABLE SYS. TAKE NOTHING FOR GRANTED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.